Update dotenv.rst

[JackPotte]

By default it tries to install an incompatible version with SF 3.4:

Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Conclusion: don't install symfony/symfony v3.4.22
    - Conclusion: remove symfony/symfony v3.4.21
...

[xabbuh]

Can you show how your composer.json file looked like when you ran that command?

[JackPotte]

It's my employer one so I can just reveal this:

    "require": {
        "php": "~7.2",
        "symfony/symfony": "~3.4",
...

[xabbuh]

Well, we could update the command to look like this:

composer require --dev symfony/dotenv:^3.4

But, I still wonder why you would want to do that in your case. The symfony/symfony package already includes the Dotenv component.

[JackPotte]

We are just migrating from SF2 to 3, and we've decided to install Dotenv in a second time.

[xabbuh]

Be careful with this though. The fact that you are able to do so is only because you are using an older version of Composer that had a bug which allowed it. Once you update to IIRC Composer 1.7.2 or higher you won't be able to install packages from the lock file you create with that anymore.

[javiereguiluz]

@xabbuh I disagree with this change. We can't do this just for one component. Also, I don't understand why we need this.

[xabbuh]

Without any version constraint Composer will try to install the version 4 of the Dotenv component. But yes we probably need to make that change in other places then too for consistency.

[OskarStark]

But you pointed out that Symfony already included the dotenv component in a working version. If they want to update it, it’s a user land problem which should not be reflected in the docs

I share the opinion of Javier and I am against merging this change.

[xabbuh]

The whole installation command is only necessary if you do not have the symfony/symfony package installed. But for these cases we should have instructions that install package versions which are compatible with the version of the docs.

[JackPotte]

@javiereguiluz so let me rephrase the bug: anyone who has SF 3.4.21 and copies the SF 3.4 dotenv installation command from the current doc will get a blocking, misleading and anxiogenic error message: "remove symfony/symfony v3.4.21"!

It's general: it has nothing to see with a particular user environment.

[OskarStark]

This should be done throughout the whole docs at once to have “consistent” state

[OskarStark]

@javiereguiluz shall the —dev option be on the end?

[javiereguiluz]

If we're going to do this, we'll need to do it for all components, so we've created #12347 to replace this one.

@JackPotte thanks for reporting this issue and I'm sorry it took us so long to deal with this.